More Science From an Easy Chair Part 6

In conclusion, let me tell of a great German sports-man, Major von Wissman, Governor of German East Africa, now no more, who came to see me at the Museum nine years ago. It was his first visit to London, and I took him to lunch at a famous grill-room. Happily, though roasting is dying out, the art of grilling still survives in this country, but nowhere else in Europe. Von Wissman said--"Can I have beer where we are going?" "Yes, certainly," I said. "German beer?" he asked. "No," I replied. "Something much better." When we were seated, I ordered a pint tankard of Reid's London stout for my friend. It was in perfect condition. He put his lips to it in doubt, but did not remove them until, with reverential drooping of the eyelids, he had emptied the tankard. "The very finest beer I have ever swallowed," he said. "What in the name of goodness is it?" I told him, and ordered him more. Soon a perfectly grilled chop and a large, clean, floury potato were before him. He proceeded to eat, and was really and unaffectedly astonished.

"But this is marvellous," he said, "wonderful! enchanting! I have never really tasted meat before in my life. Reitzend! Colossal!" He had a steak to follow, and I was pleased to have been able to show him something which I knew (by experience of that city) they could not produce in Berlin. Three days later I went over to the same hospitable grill-room for a chop, and told the gifted grill-cook (the French, in former centuries, had a proverb, "Anyone may learn to be a cook, but one must be born a 'rotisseur'") of the admiration he had excited in the Emperor William's friend. "Yes, sir," he said, "I fancy he did like it, for he came here by himself yesterday and the day before, and took the same grills and stout." Von Wissman was staying at the German Emba.s.sy, but was drawn all the way to South Kensington by the sweet savour of the grill-room--an instance of what the physiologists call "positive chemotaxis."

What I have here written on food and cookery is no "gourmet's" praise of indulgence in the pleasures of the table, nor is it an expression of a mere personal preference. It is a protest, based on scientific grounds, against the neglect of one of the bulwarks of health--the honest traditional cookery which flourished in London forty years ago.

CHAPTER X

SMELLS AND PERFUMES

The old saying, "_De gustibus non disputandum_," is based upon the fact that both liking and the repulsion evinced by human beings for different odours (including those odours which we call flavours) are not matters of general agreement. Thus the smells of garlic and of onions, and even of a.s.safoetida, are to many men among the most attractive and appetising in existence--to very many they are, on the other hand, repulsive. High game, a certain kind of putrid fish ("Bombay ducks"), and again rotten cheese are attractive to many men and offensive to as many more. Many animals revel in the smell and flavour of carrion, and even of manure, which they devour. There are well-known flowers which attract insects, not by the possession of the sweet perfumes appreciated and extracted by mankind, but by a smell like that of putrid meat, which so far misleads blue-bottle flies as to cause them to lay their eggs on the reeking blossom. So diverse are the tastes of men and animals in these matters that it is remarkable when we find agreement among them, as, for instance, in the attraction for b.u.t.terflies of those delicate scents which also are agreeable to ourselves in such flowers as the rose, the jasmine, the heliotrope and the honeysuckle.

There seems to be no rule or principle at work by which smells can be definitely cla.s.sed as either pleasant or unpleasant. Even perfumes carried by some of the inhabitants of Western Europe with the intention of making themselves attractive to their fellow-citizens are often repulsive to a certain proportion of those who come near them, as, for instance, is the case with the extract of the East Indian herb "patchouli." In regard to our other senses there is a general agreement amongst mankind, which extends also to all animals, as to what is agreeable and what is disagreeable. There are definite mathematical laws as to harmony and melody in sound and colour which affect animals and ourselves to a large extent similarly. Sweets are agreeable and bitters are disagreeable, though it is the fact that the snail, which loves sugar, recoils from saccharine, and there are "mites" (_Acari_) which feed with avidity on bitter strychnine! Excess of heat and of cold is disliked by animals and all men, whilst the sense of touch is pleasurably or painfully affected in much the same way in most men and animals, more than is the case with regard to any other of the senses. The sense of smell depends upon immediate and personal experience of "a.s.sociation" for the determination of pleasure or pain, attraction or repulsion, as the result of its being called into operation. It is a very general experience that odours are more efficient in arousing memory than are mere colour effects or sounds.

Not only in animals with acutely developed olfactory powers, but also in man, an odour--a peculiar perfume--will start a whole chain of reminiscence when sight and sound have failed to do so. It is due to this close a.s.sociation with memory (conscious or unconscious) that an odour is agreeable or disagreeable.

In itself an odour is neither attractive nor repulsive. The acrid fumes of sulphur, chlorine, ammonia, and such bodies are not simply "odours" but corrosive chemical vapours, which act painfully upon the nerves of common sensation within the air-pa.s.sages of the nose and throat and not exclusively, if at all, on the terminations of the olfactory nerves. An odour--that which acts on the special nerves of smell distributed in chambers of the nose--acquires its attractive or its repulsive quality only as the result of mental a.s.sociation with what is beneficial (suitable food, mates, friends, safety, home, the nest), or with what is injurious (unsuitable food, poison, enemies, danger, strange surroundings, solitude). Hence it is intelligible that the man accustomed to garlic or onions in his food is strongly attracted by their smell. So too the man whose tribe or companions have learnt by necessity to eat slightly putrid meat, fish, and cheese is attracted by their odour, though for others these odours are a.s.sociated rather with what is poisonous and injurious. The dislike of the smell of sewer-gas and foul acc.u.mulations of refuse was not known to former generations of men (even in European cities a couple of hundred years ago) any more than it is to-day to the more unfortunate poorer cla.s.ses, to many modern savages, to hyenas, and several other animals and birds which inhabit lairs and caves which they make foul.

The odour of putrescence has become actually painful and almost intolerable to the more cleanly cla.s.ses of mankind, owing to the a.s.sociation with it, as the result of education, of fear of disease and poisoning. Either conscious or unconscious a.s.sociation of an odour with what is held, either as the result of tradition or through personal experience, to be beneficial and of pleasant memory, or, on the contrary, injurious and of painful connection, determines man's liking for and choice or rejection of, odours and flavours. One can account with fair success on this basis for one's own preferences and dislikes in the matter.

On the other hand, odours exist in vast variety amongst plants and animals which have not acquired any special a.s.sociation or significance. We find that some organisms produce as a result of their chemical life material which oxidises and gives out light and so these organisms are "phosph.o.r.escent" without any consequence, good or bad, to themselves. And then we come upon others (as, for instance, the glow-worms and fire-flies) which have made use of this "accidental"

quality, and produce phosph.o.r.escent light in special organs so as to attract the opposite s.e.x. Again, we find that the red-coloured oxygen-seizing crystalline substance haemoglobin exists in the blood of a vast number of animals, and might as well be green or colourless for all the good its colour does them. Yet here and there the splendid red colour which this chemical gives to the blood becomes of great importance as a "decoration," or "s.e.x-ornament." The comb of the domestic fowl, the wattles of the turkey, but above all the supreme beauty of the human race--the cherry-red lips and the crimson-blus.h.i.+ng cheek of healthy youth--owe their wonderful colour to the red blood which flows through them. So at last the redness, of the oxygen-carrier is turned to account. So it must be also with odorous substances. Many have been called into existence, but few have been chosen in the long course of animal evolution and selected as the important means of repulsion or attraction.

There are odorous substances attached to many of the lower animals which seem to have no significance, but just happen to be the result of necessary chemical changes, not aimed (so to speak) at their production. Of course, it is very difficult to form a certain and definite conclusion as to their uselessness as odours. For instance, nearly all the sponges when fresh and filled with living protoplasm have a curious smell which reminds one of that given off by a stick of phosphorus. Marine sponges have it and so has the beautiful green or flesh-coloured liver sponge (common on the wood of rafts and weirs in the Thames). A rather uncommon marine worm, called _Balanoglossus_ or the acorn worm, has a very strong and unpleasant smell like that of iodoform. In neither case is the nature of the odorous body known, nor its use to the animal suggested. Smelts smell like cuc.u.mbers: the green-bone fish and the mackerel smell alike. One of the common earth-worms has a strong aromatic smell, and the common snail, as well as the sea-hare and one of the cuttle-fishes (_Eledone_), smells like musk. Musk itself is produced, as a scent attracting the opposite s.e.x, by several animals--musk-deer, musk-sheep, musk-rats. I am not now attempting to enumerate the well-recognised odours of animals such as are extracted from them by man in order to "opsonize" himself, but am pointing to the more obscure cases. There is not a very great or marked variety in the odours of fishes; but reptiles with their dry, oily skins give off various aromatic smells, none of which are valued by man. Toads have distinct odours, and one kind (_Pelobates fuscus_, or the heel-clawed toad), common in Europe, but not British, is known locally as the garlic toad on account of its smell. There are amongst carnivorous mammals various smells allied to that of civet which are not so agreeable to man as that substance; for instance, the odour of the fox and of the badger, and yet more celebrated, the terrible, awe-inspiring smell of the fluid emitted in self-defence by the skunk from a sac in the hinder part of the body. Horses, cows, goats, sheep, and the giraffe have their distinctive odours. Many of the herbivorous animals secrete a colourless fluid from large glands opening on or near the feet, and also from a gland in front of the eye (similar glands occur in other strange positions), which has not a smell familiar to man--that is to say, not one which has been recognised and described--yet seems to be readily "smelt" by the animals of its own kind. The bats--especially the large frugivorous bats--have a very unpleasant, frowsy smell.

An important fact about animal smells is that many which we might be inclined to attribute to the animal which diffuses them, are really due to the fermentative or putrefactive action of bacteria which swarm on the skin and in the intestines of animals. It is often difficult to decide how far a peculiar animal odour is due directly to a substance secreted by the animal, and how far the odour of that substance is modified or even entirely produced by the chemical changes set up in secretions of the body-surface by bacteria. Several distinct repulsive smells liable to occur on the human body are due to want of cleanliness in destroying bacteria by proper antiseptics. The fatty and waxy secretions of the skin are often decomposed by bacteria, even before complete extrusion from the glands in which they are formed, whilst the decomposition of food in the mouth and intestines by bacteria alters materially both the natural odour of the animal's breath and the smell of the intestinal contents. In young and healthy animals in natural conditions there is some check--it is not easy to say what--upon the putrefactive activities of the omnipresent bacteria. The skin of a healthy young animal has a pleasant odour, and its breath (notably in the case of the cow and the giraffe) is naturally sweet-smelling. The same should be the case, under perfectly healthy conditions, with human beings.

There is one important cause of animal odours and flavours upon which I have not hitherto touched. Many animals acquire an odour or flavour directly from the food upon which they feed. Certain odorous bodies are in the food and are taken up into the blood of the consuming animal unchanged, and are then thrown out by secreting glands on the skin. This is the case with the odorous substance of onions. People do not smell of onions after they have eaten them in consequence of particles of onion remaining in the mouth. The volatile odoriferous matter of the onion is absorbed into the blood. It pa.s.ses out first through the lungs and later through the small fat-forming glands in the skin. It is difficult to ascertain how far animals derive their odours in this way in a complete state from their food, and how far they chemically construct them afresh by their own activity. No doubt both processes occur; but in plants the odorous bodies are built up entirely by the chemical action of the plant itself upon simple salts of carbonic acid, ammonia and nitrates. Animals can certainly take highly elaborated chemical bodies into their digestive organs without destroying them and absorb them unchanged into the blood and deposit them in the tissues. Thus the canary is made to take up the red colour of cayenne pepper and deposit it in the feathers. Thus the green oysters of Marennes acquire their colour from minute blue plants (diatoms) on which they feed. And thus, too, the canvas-backed ducks of the United States take into their tissues the odorous matter of celery, and our own grouse the flavour of heather, whilst fish-eating birds and whales in this way acquire a fishy taste. So, too, the flounders and the eels of the Thames, and even salmon in muddy rivers, acquire a taste like the smell of river mud. It is probable that many of the odours of animals (but by no means all) are thus derived directly from their food, or are produced by very slight changes of the odorous bodies absorbed in food. Mutton and beef owe their savour in some degree to the scents of the gra.s.ses on which sheep and oxen feed. And it is not improbable that the sheep-like smell which the Chinese detect in the European, comes to the latter direct from his general use of the sheep as food.

Plants are the great chemical manufacturers in the world of life, and second to them come our human industrial and scientific chemists. And though we must claim for animals some power of manufacturing distinct odorous bodies from inodorous nutritive matter a.s.similated by them, it is probable that in many cases the odour which is characteristic of an animal is derived by no very complicated change from odorous bodies existing in its habitual food.

A curious case of a substance valued as perfume by civilised man, and yet coming from a source whence sweet odours would hardly be expected, is that which is known as "ambergris," or "ambre gris" (grey amber).

It is still used in the manufacture of esteemed perfumes, and is sold at five guineas the ounce. It is found floating on the surface of the ocean, and is a concretion of imperfectly digested matter from the intestine of a whale--probably the sperm-whale. It is a grey, powdery substance, and in it are embedded innumerable fragments of the h.o.r.n.y beaks and sucker-rings of cuttle-fishes--creatures which form the chief food of the sperm-whale and other toothed whales. I have already mentioned above that one of our common cuttle-fishes (the _Eledone moschata_) has a strong odour of musk, and it is possible that ambergris owes its perfume to the musk-like scent of the cuttle-fish eaten by the whale in whose intestine it is formed. Another "smell"

which is extremely mysterious is that produced by two quartz-pebbles, or even two rock-crystals, or two pebbles of flint or of corundum, when rubbed one against the other. A flash of light is seen, and this is accompanied by a very distinct smell, like that given out by burning cotton-wool. It is demonstrated--by careful chemical cleaning before the experiment--that this is not due to the presence of any organic matter on or in the stones or crystals used. It seems to be an exception to the rule that "odours" (as distinct from pungent vapours or gases) are only produced by substances formed by plants or animals.

Perhaps that is not so completely a rule as I was inclined to think.

It is true that one can distinguish the "smells" of chlorine, of bromine, and of iodine from one another. And there are statements current as to the distinctive smells of metals--though they may possibly be due to the action of the metals on organic matter. In any case it seems, according to our present knowledge, that the smell given out by the rubbing of pieces of silica (quartz, flint, etc.) is due to particles of silica (oxide of silicon) volatilised by the heat of friction, which are capable of acting specifically on the olfactory sense-organ.

CHAPTER XI

KISSES

"Among thy fancies, tell me this, What is the thing we call a kiss?

I shall resolve ye what it is."

--Robert Herrick

Kissing is an extremely ancient habit of mankind coming to us from far beyond the range of history, and undoubtedly practised by the remote animal-like ancestors of the human race. Poets have exalted it, and in these hygienic days doctors have condemned it. In the United States they have even proposed to forbid it by law, on the ground that disease germs may be (and undeniably are in some cases) conveyed by it from one individual to another. But it is too deep-rooted in human nature, and has a significance and origin too closely a.s.sociated with human well-being in the past, and even in the present, to permit of its being altogether "tabooed" by medical authority.

There are two kinds of "kissing" practised by mankind at the present time--one takes the form of "nose-rubbing"--each kiss-giver rubbing his nose against that of the other. The second kind, which is that familiar to us in Europe, consists in pressing the lips against the lips, skin, or hair of another individual, and making a short, quick inspiration, resulting in a more or less audible sound. Both kinds are really of the nature of "sniffing," the active effort to smell or explore by the olfactory sense. The "nose-kiss" exists in races so far apart from one another as the Maoris of New Zealand and the Esquimaux of the Arctic regions. It is the habit of the Chinese, of the Malays, and other Asiatic races. The only Europeans who practise it are the Laplanders. The lip-kiss is distinguished by some authorities as "the salute by taste" from nose-rubbing, which is "the salute by smell."

The word "kiss" is connected by Skeat with the Latin "gustus," taste; both words signify essentially "choice." But it would be a mistake to regard the lip-kiss as merely an effort to taste in the strict sense, since the act of inspiration accompanying it brings the olfactory pa.s.sages of the nose into play. Lip-kissing is frequently mentioned in the most ancient Hebrew books of the Bible, and it was also the method of affectionate salutation among the Ancient Greeks. Primarily both kinds of kissing were, there can be no doubt, an act of exploration, discrimination, and recognition dependent on the sense of smell. The more primitive character of the kiss is retained by the lovers' kiss, the mother's kissing and sniffing of her babe, and by the kiss of salutation to a friend returning from or setting out on a distant journey. Identification and memorising by the sense of smell is the remote origin and explanation of those kisses. The kissing of one another by grown-up men as a salutation was abandoned in this country as late as the eighteenth century. "'Tis not the fas.h.i.+on here," says a London gentleman to his country-bred friend in Congreve's "Way of the World." But we have, most of us, witnessed it abroad, and perhaps been unexpectedly subjected to the process, as I once was by an affectionate scientific colleague. Independently of the more ordinary practice of kissing--there is the "ceremonial kiss"--the kissing of hands, or of feet and toes, which still survives in Court functions--whilst the Viennese and the Spaniards, though they no longer actually carry out their threat, habitually startle a foreigner by exclaiming--"I kiss your hands." The Russian Sclavs are the most profuse and indiscriminate of European peoples in their kissing. I have seen a Russian gentleman about to depart on a journey "devoured"

by the kisses of his relations and household retainers, male and female. Among the poor in rural districts in Russia this excessive habit of kissing leads to the propagation of the most terrible ulcerative disease among innocent people--as related by Metchnikoff in the lectures on modern hygiene which he gave in London some seven or eight years ago (published by Heinemann).

We may take it, then, that the act of kissing is primarily and in its remote origin an exploration by the sense of smell, which has either lost its original significance, and become ceremonial, or has, even though still appealing to the sense of smell, ceased to be (if, indeed, it ever was so) consciously and deliberately an exercise of that sense. This leads us to the very interesting subject of the sense of smell in man and in other animals. There is no doubt that the sense of smell is not so acute in man as it is in many of the higher animals, and even in some of the lower forms, such as insects. It is the fact that so far as we can trace its existence and function in animals, the sense of smell is of prime importance as distinguis.h.i.+ng odours which are a.s.sociated either with objects or conditions favourable to the individual and its race, or, on the other hand, hostile and injurious to it. It never reaches such an extended development as a source of information or general relation of the individual to its surroundings as do the senses of sight, hearing and touch. It depends for its utility on the existence of odorous bodies which are not very widely present, and are far from universal accompaniments of natural objects. Apart from some pungent mineral gases, all odorous bodies are of organic origin. Even as recognised by the less acute olfactory sense of man, the number and variety of agreeable and of disagreeable scents, produced by various species of animals and plants, is very considerable. But there is no doubt that the number and variety discriminated by such animals as dogs and many of the other hairy, warm-blooded beasts is far greater. The nature of the particles given off by odorous bodies which act on the nerve-endings of the organs of smell of animals, is remarkable. They are volatile; that is to say, they are thrown off from their source and float in the air in a state of extreme subdivision. Unlike the particles which act upon the nerves of taste, they are not necessarily soluble in water, and though often spread through and carried by liquids, are in fact rarely dissolved in water. The dissolved particles which act upon the nerves of taste can be distinguished by man into four groups--sweet, sour, bitter, and saline. But no such cla.s.sification of "smells" is possible. As a rule mankind confuses the "taste" of things with their accompanying "smell." The finer flavours of food and drink not included in the four cla.s.ses of tastes are really due to odoriferous particles present in the food or drink, which act on the terminations of the olfactory nerves in the recesses of the nose, and excite no sensation through the nerves of taste.

The part of the brain from which the nerves of smell arise is of relatively enormous size in the lower vertebrates--as much as one fifth of the volume of the entire brain in fishes--a fact which seems to indicate great importance for the sense of smell in those forms.

Even in the mammals (the hairy, warm-blooded, young-suckling beasts) the size of the olfactory lobes of the brain and of the olfactory nerves, and the labyrinthine chambers of the nose on which the nerves are spread, is very large, as one may see by looking at a mammal's skull divided into right and left halves. And it seems immoderately large to us--to man--because, after all, so far as our conscious lives are concerned, the sense of smell has very small importance. Yet man has a very considerable set of olfactive chambers within the nostrils and has large olfactory nerves. Not rarely men and women are found who are absolutely devoid of the sense of smell, and the same thing occurs with domesticated cats and dogs. In these cases the olfactory lobes of the brain are imperfectly developed. It is found that men in this condition suffer but little inconvenience in consequence. We are able, through their statements, to ascertain what parts of the savoury qualities of food and drink belong to taste and what to smell. Such individuals do not perceive perfumes, the bouquet of wine, or the fragrance of tobacco, nor can they appreciate the artistic efforts of a good cook. But they are spared the pain of foul smells, and possibly in this way they may incur some danger in civilised life through not being able to detect the escape of sewer-gas or of coal-gas into a house, or the putrid condition of ice-stored fish, birds, and meat. A friend of my own, who is devoid of the sense of smell, inherited this defect from his father, and has transmitted it to some of his children. I was surprised to find in conversing with him how often I alluded to smells, either pleasant or unpleasant, when (as we had agreed he should) he would interrupt me and say that my remark had no meaning for him.

Some have a far more acute sense of smell than others, and again some men, probably without being more acutely endowed in that way, pay more attention to smells, and use the memory of them in description and conversation. Guy de Maupa.s.sant is remarkable as a writer for his abundant introduction of references to agreeable and mysterious perfumes, and also to repulsive odours. But some men certainly have an exceptionally acute sense of smell, and can, on entering an empty room, recognise that such and such a person has been there by the faint traces--not of perfumery carried by the visitor--but of his individual smell or odour. This brings us to one of the most important facts about odorous bodies and the sense of smell, namely, that not only do the various species of animals (and plants) each have their own odour--often difficult or impossible for man, with his aborted olfactory powers, to distinguish--but that every individual has its own special odour. As to how far this can be considered a universal disposition is doubtful. It is probable that the power of discriminating such individual odours is limited (even in the case of dogs, where it is sometimes very highly developed), to a power of discriminating the distinctive smells of the individuals of certain species of animals, and not of every individual of every species.

Everyone knows of the wonderful power of the bloodhound in tracking an individual man by his smell, but dogs of other breeds also often possess what seems to us extraordinary powers of the kind. On a pebbly beach I pick up one smooth flint pebble as big as a walnut. It is closely similar to thousands of others lying there. I hold it in my hand without letting my fox-terrier see it, and then I throw it. It drops some eighty yards off among the other pebbles, and I could not myself find it again. But the dog runs forward, notes vaguely by ear and by eye the spot where it strikes, and then commences a systematic circling within about ten yards of the spot. In half a minute he pounces with the utmost a.s.surance on to one selected stone, and brings it to me. It is invariably the stone which had been in my hand, unseen by the dog, thrown by me, and detected by the smell I have communicated to it.

Not only is the discrimination of individuals by the sense of smell a very astonis.h.i.+ng thing, but so also is the obvious fact that the total amount of odoriferous matter which is sufficient to give a definite and discriminative sensation through the organ of smell is of a minuteness beyond all calculation or conception. These two facts--the almost infinite individual diversity of smell and the almost infinite minuteness of the particles exciting it--render it very difficult to form a satisfactory conclusion as to the nature of those particles. It has been from time to time suggested that the end organs of the olfactory nerves may be excited, not by chemically active particles, but by "rays," olfactive undulations comparable to those of light.

Physicists have not yet been able to deal with the problem, but the recent discoveries and theories as to radio-active bodies such as radium may possibly lead to some more plausible theory as to the diffusion and minuteness of odorous particles than any which has yet been formulated. An example of the minuteness of odoriferous particles is afforded by a piece of musk which for ten years in succession has given off into the changing air of an ordinary room "particles"

causing a readily recognised smell of musk, and yet is found at the end of that time to have lost no weight, that is to say, no weight which can be appreciated by the finest chemical balance. An a.n.a.logy (I say only an a.n.a.logy, a resemblance) to this is furnished by a pinch of the salt known as radium chloride, no bigger than a rape-seed, and enclosed in a gla.s.s tube, which will continue for months and years to emit penetrating particles producing continuously without cessation most obvious luminous and electrical effects upon distant objects, the particles being so minute that no loss of weight can be detected in the pinch of salt from which they are given off.

The sense of smell is of service to animals--

(1) In avoiding enemies and noxious things.

(2) In tracing and following and discriminating prey or other food.

(3) In recognising members of their own species and individuals of their own herd or troop, and in finding their own young and their own nests.

(4) In seeking individuals of the opposite s.e.x at the breeding season.

It is in connection with the last of these services that we come across some of the most curious observations as to the production and perception of odorous particles. b.u.t.terflies and moths and some other insects have olfactory organs in the ends of the antennae and the "palps" about the mouth. The perfumes of flowers have been developed so as to attract insects by the sense of smell, as their colours have been also developed to attract insects by the eye. The insects serve the flowers by carrying the fertilizing pollen from one flower to another, and thus promoting cross-fertilization among separate individual plants of the same species. But probably concurrently with this has grown up the production of perfume by the scales on the wings of moths and b.u.t.terflies--perfumes which have the most powerful attraction for the opposite s.e.x of the same species. Curiously enough (for these perfumes might very well exist without being detected by man) some of the perfumes produced by b.u.t.terflies are "smellable" by man. That of the green-veined white is described as resembling the agreeable odour of the lemon verbena. It is produced by certain scales on the front border of the hinder wings of the male insects, and not at all by the females, who are, however, attracted by it, and flutter around the sweet-smelling male. Other male b.u.t.terflies produce a scent like that of sweet briar, others like honeysuckle, others like jasmine, and so attract the females. Other b.u.t.terflies are known which produce repulsive odours, and so protect themselves from being eaten by birds and lizards. Again, there are moths (for instance, the emperor moth, Saturnia), the females of which produce a perfume which attracts the males, and is of far-reaching power. The French entomologist, Fabre, placed one of these female moths in a box covered with net-gauze, and left it in a room with open window, facing the countryside. In less than an hour the room was full of male emperor moths--more than a hundred arrived, although none had been previously visible in the neighbourhood. They crowded over the box, and even afterwards, when the female moth had been removed, the perfume remained in the box, and the male moths eagerly sought it. The perfume must have carried far from the room where the female was, out into the woods where it was perceived, and followed up to its source by the male moths.

Such perfumes are very generally produced by little pockets or glands in the skin, the secretion having, in the case of insects, birds and mammals, an oily nature. In mammals they are largely produced by both males and females, and serve to attract the s.e.xes to one another.

Hairs are situated close to the minute odoriferous glands and serve an important part in acc.u.mulating and diffusing the characteristic perfume. Musk and civet are of this nature, and it is a significant fact that these substances are used as perfumes by human beings. It would seem as though mankind had lost either the power of satisfactorily perceiving the perfumes naturally produced by the human skin, or that the production of such perfumes had for some reason diminished. Either condition would account for the use by mankind of the perfumes of other animals and of flowers. There are a variety of odorous substances produced by different parts of the human body, of which some are agreeable and others disagreeable. One of the most curious facts in regard to odorous bodies is the close resemblance between agreeable and repulsive odours, and the readiness with which the judgment of human beings may p.r.o.nounce the same odour agreeable at one period or place, and disagreeable at another. There also seems to be a "dulling" of the power to perceive an odour which is a consequence of constant exposure to that odour. Thus the Chinese say that Europeans all smell unpleasantly, the odour resembling that of sheep, although we do not observe it; whilst Europeans notice and dislike the smell of the negro, a smell of the existence of which he is unaware. The blood of animals, including that of man, has, when freshly shed, a smell peculiar to the species, which has not, however, any resemblance to that of the skin or of the waxy glands of the same animal.

It seems that in regard to the exercise of the sense of smell by man, we must distinguish not only greater from less acuteness and variety of perception, but in the case of this sense-organ, as in regard to the others, we must distinguish "unconscious" from "conscious"

sensation. All our movements are guided and determined by sensations to touch and sight, and to some extent, of hearing, of which we are unconscious. A vast amount of our sense-experience comes to us and is recorded without our having consciousness of anything of the kind going on. It is probable that the world of smells in which a dog with a fine olfactive sense lives, produces little or nothing in the dog's mind which is equivalent to our conscious perception of degrees of agreeable and disagreeable odours. The dog is simply attracted and repulsed in this direction and in that by the operation of his olfactive organs, without, so to speak, giving any attention to the sensation which is guiding him or being "aware" of it. No doubt at times, and with special intensities of smell, he is, in his way, conscious of a specific sensation. It is probable that whilst man's general acuteness in perceiving and discriminating smells has dwindled (as has that of the apes) in comparison with what it was in his remote animal ancestry, yet he retains a large inherited capacity of unconscious smell-sense, which most of us are unable to recognise, although it is there, operating in ourselves unknown to us and un.o.bserved. The consciousness of smell-sensations is what we value and talk of. It does not extend to the more primal smell-excitations, except in extraordinary individuals. Thus, it seems to be not improbable that we are attracted or repelled by other human individuals by the unconscious operation upon us of attractive or repulsive odours, and that the unaccountable liking or disliking which we sometimes experience in regard to other individuals is due to perfumes and odours emanating from such persons, which act upon us through our olfactory organs without our being conscious of the fact.

It seems that we can thus arrive at a probable explanation of the universality of the habit of kissing, and of "what is that thing we call a kiss." It is not consciously used among civilised populations as a deliberate attempt to smell the person kissed, but it nevertheless serves to allow the unconscious exercise of smell-preference, testing, and selection, with which are mingled, more or less frequently, moments of conscious appreciation of the complex of odours appertaining as an individual quality to the person kissed.

CHAPTER XII

LAUGHTER

The ancients a.s.sociated laughter with the New Year. I am not sure whether or no it is of good omen to begin the New Year with laughter.

Omens are such tricky things that I have given up paying any attention to them. One would think it might be held to be unlucky to stumble on the doorstep as you set out from home, but the old omen-wizards, apparently from sheer love of contradiction, said, "Not at all! It is unlucky to stumble as you come into the house, and therefore it is lucky to stumble as you go out!"